JVM crash when calling to and from Javascript from a WebEngine

When using a WebEngine and calling from Javascript a Java function that calls a Javascript function, the JRE crashes (see the code for the exact situation)

---- Begin code
import netscape.javascript.JSObject;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Worker.State;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebView;
import javafx.stage.Stage;

public class Main extends Application {

    public static void main(String[] args) {
        Application.launch(Main.class);
    }
    
    public class ParentFunctions {
        public void parentfunc(final JSObject obj) {
            Platform.runLater(new Runnable() {

                @Override
                public void run() {
                    obj.call("success");
                }
            });
        }
    };
    
    @Override
    public void start(Stage stage) throws Exception {
        final WebEngine engine = new WebEngine();
        engine.loadContent("<script type='text/javascript'>function init(javaobj) { javaobj.parentfunc({ success : function() {document.write('success');} }); }</script>");
        engine.getLoadWorker().stateProperty().addListener(new ChangeListener<State>() {
            @Override
            public void changed(ObservableValue<? extends State> paramObservableValue, State paramT1, State newState) {
                if(newState == State.SUCCEEDED) {
                    JSObject window = (JSObject) engine.executeScript("window");
                    
                    window.call("init", new ParentFunctions());
                }
            }
        });
    }
}
---- End code

I'm not sure I can attach files, so I haven't included the crash log.